<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			.xiangXiaSanJiao {
				width: 0;   /*数值0可以省略单位*/
				height: 0;
				border-top:  50px solid #f00;
				border-right:  50px solid  transparent;
				/* border-bottom:  50px solid #00f; */
				border-left:  50px solid  transparent;
			}
		</style>
	</head>
	<body>
		<div class="xiangXiaSanJiao"></div>
		<div class="xiangShangSanJiao"></div>
		<div class="xiangZuoSanJiao"></div>
		<div class="xiangYouSanJiao"></div>
	</body>
</html>
